General comment

Comparing MRS and OVS it looks as though *hí• (‘arrive there’??) is
originally compounded with *ki (probably ‘reciprocal’) and when this
contracted to *k-hi• and became opaque a new stem *hpa was added. Now
this augmented stem can be “reciprocalized” in DH by prefixing yet another
*hki. DH kh rather than hk is predicted, so analogy has played a role
here; the earlier *khi has been reinterpreted as a simple ‘reciprocal’.